RNA is Single-Stranded

RNA
is a polymer of nucleotides that's similar to DNA. The
biggest difference between RNA and DNA is that RNA is
a single stranded molecule while DNA is double stranded
(a double helix).

Another
difference is that RNA does not use thymine as a nucleotide
base, instead, it uses a base called uracil. Uracil
can form a base pair with adenine in RNA, just like
thymine does in DNA. Here is a summary of the differences
between RNA and DNA.

Characteristic

DNA

RNA

Structure

double-stranded

single-stranded

Bases

Adenine,
cytosine, guanine, thymine

Adenine,
cytosine, guanine, uracil

Sugar

deoxyribose

ribose

The
fact that RNA is single stranded allows it to assume
various unique shapes.

There is no second strand to
lock it into a double helix shape. It can form base
pairs with itself, and this allows it to fold up into
many different three-dimensional shapes.